Rapid fine-grained copper electrodeposition



Patented Sept. 30, 1952 Company; Cleveland,

Copper plating by means of copper cyanide is quite'anoldindustry; andfrom time to time de' tailed improvements in' bath compositions havebeen suggested, such as" the Rochelle salt'copper bath, pyrophosphatecopper, etc., but a'fun'damental handicap has remained that plating.could notbe operated at high current'densities as desirable' for volumeproduction. Even plating with as'low'a's 12-15 amperes per sq. ft.has'resulted'in'd'eposits moreor less rough and pitted if'a thickness0.001" or more was required. A' bath vfor electrodeposition which canpermit high operating rates, with current densities of 30 or moreamperespersq. ft., and with production of bright 'fine grained deposits hasaccordingly been much desired in theindustry. .In accordance with thepresent invention, an improved electrodeposition thus with high currentdensity and volume production of smooth fine-grained bright deposits insuchthicknesses as may be desired, is now possible Other objects andadvantages of the invention will appear in the following description.

To the'accompli'shment of the foregoingand related ends, theinventionthencomprisesfihe features hereinafter fully described,andfpj'a'rtieularly pointed out in the claims, the followin'gdescription setting forth in'detail certain illustrative embodiments oftheinvention, these being indicative however of but a few of the variousways in which thepprinciple of theinvention may be employed.

In general, copper is supplied by a bath of copper cyanide type, and ofalkaline category. Fundamentally, in the present invention the bath isprovided with a reaction product of a diazo salt and sulphur, suchproduct being dissolved and made up with the desired copper cyanide andother ingredients for the operating bath.

For the preparation of the diazo derivative, the starting point is aprimary arylamine, preferably anthranilic acid, but there may be alsoapplied aniline and its homologs, the toluidines and xylidines, alsobenzylamine, etc. Thus for instance the anthranilic acid or otherarylamine is made up in an acid solution, for instance hydrochloric,although sulphuric or other equivalent mineral acids may be used, thensodium nitrite or equivalent diazotizing agent in solution is applied.The diazo salt as thus provided in solution is reacted with sulphur in aprecipitating form, such as hydrogen sulphide, sodium sulphide, etc.Conveniently, hydrogen sulphide is passed into the solution for aroundtwo hours,

hi0; a corporation of Application spmtai2s;.1948;; Serial-No. 51,639

(;laims. (o1. em -52) or" as necessary to complete precipitation. The

resulting precipitatei which may be designated" a reaction product ofasulphide on a diazosalt of a primary 'arylami'ne, is vacuum-filtered asdryaspossible; and the filter cake is dissolved and withfiurtheradvantage is; boiledin' water containingt triethanolamine. After coolingand filtering, theffiltr'atemixed D coppencyanide, sodium cyanideandsod'ium hy dioxide; and is boiled, cooled'and filt'eredi a' wettingagent; such'for instance as a sulphate of a longchain alcohol,preferablyof 1 0'-14- car bon atoms, dioctyl sodium sulphosuccinate, al-

karyl sodium su'lphonates; etc: is'added, and degallon or 3.785 liters.

sirably the final volume is made" up withaddi-- tionof water asnecessary," to a convenient concentration stock solution. A'desiredamount of this concentrationis: addedtothe cyanide coppe bath whichisto'be-op'erated;

With" such bath, high current density is 'em'-' ployed; conveniently3Q-50' a'mperes per sq; ft: The copper'deposited" is smooth,fine-grained, and bright, and thickness of. 01001 can thus be readilyobtained in: about 15' minutes. j

'FOI" example: '1'.08 kg? of anthranilic acid is dissolved inf1'.62liters of water and 1 .19- of concentratedhydrochloric'acid. Then 810'gms: of sodium nitrite in 7.6' liters of water is added. Aiter thediazotizing action is completed, a stream of hydrogen sulphide is passedthrough thesolution for" about two hours; The resulting' precipitate isfiltered and vacuum sucked dry as much as possible. Thissulphide-precipitated diazo compound provides the active agent in myhigh-speed plating bath. The filter cake is then dissolved and boiledfor about 30 minutes in a solution of 5.8 liters of triethanolamine in29 liters of water. The solution is cooled and filtered. The filtrate ismixed with 10.16 liters of a solution of the following composition: 392gms. of copper cyanide and 438 gms. of sodium cyanide and 99 gms. ofsodium hydroxide per to a boil, then cooled and filtered. And to thefiltrate 210 cc. of a sulphate of long chain alcohol wetting agent isadded and the final volume is made up to 24 gallons or 90.84 liters.This stock solution is then employed by adding to the copper cyanidebath for operation. For instance, to cc. of the stock solution is addedfor each gallon of any copper cyanide electrodeposition Other modes ofapplying the principle of the invention may be employed, change beingmade as regards the details described, provided the with'a solution-- ofThis mixture is brought,

features stated in any of the following claims, or the equivalent ofsuch, be employed.

I therefore particularly point out and distinctly claim as my invention:

1. In a process of preparing a bath for electrodepositingcopper,dissolving anthranilic acid in hydrochloric acid solution, reacting uponthe same with a diazotizing agent, then precipitating by Has,de-watering the precipitate, dissolving the precipitate and water,cooling, filtering, containing copper cyanide, sodium cyanide and sodiumhydroxide, boiling, cooling, filtering, adding a wetting agent, makingto a stock volume with water, and adding a minor proportion of suchstock solution to an electrodeposition bath containing copper cyanide,sodium cyanide and sodium hydroxide.

. 2. In a process of preparing a bath for electrodepositing copper,forming a diazo salt of a primary arylamine of the group consisting ofanthranilic acid, aniline, toluidines, xylidines and benzylamine, in amineral acid solution, precipitating by hydrogen sulphide, de-wateringthe precipitate, dissolving the precipitate and boiling intriethanolamine and water, cooling, filtering, mixing with a solutioncontaining copper cyanide, sodiumcyanide and sodium hydroxide, boiling,

' cooling, filtering, adding a wetting agent, making to a stock volumewith water, and adding a minor proportion of. such stock solution to anelectrodeposition bath containing copper cyanide, sodium cyanide andsodium hydroxide.

, 3. In a process of preparing a bath for electrodepositing copper,forming a precipitate by reacting on a solution of diazo salt of aprimary arylamine of the group consisting of anthranilic acid, aniline,toluidines, xylidines and benzylamine, with a sulphide precipitant ofthe group consisting of hydrogen sulphide and sodium-sub boiling intriethanolamine and mixing with a solution arylamine of the groupconsisting of anthranilic acid, aniline, toluidines, xylidines andbenzyiamine, by a sulphide precipitant of the group consisting ofhydrogen sulphide and sodium sulphide, de-watering the precipitate,dissolving the precipitatein water containing triethanolamine, andsupplying such solution to a'copper cyanide electrodeposition bath. 5.In a process of the character described, electrodepositing copper from asolution which contains copper cyanide, sodium hydroxide, and a reactionproduct of a sulphide of the group consisting of hydrogen sulphide andsodium sulphide on a diazotized primary arylamine of the groupconsisting of anthranilic acid, aniline, toluidines, xylidines andbenzylamine, said reaction product as a precipitate being dissolved inwater containing triethanolamine.

6. A plating bath of aqueous copper cyanide and sodium hydroxide,including the reaction product of a sulphide of the groupconsisting ofhydrogen sulphide and sodium sulphide on diazotized anthranilic acid,said reaction product as a precipitate being dissolved in watercontaining triethanolamine. V v

'7. An electrodeposition bath including copper cyanide, sodiumhydroxide, and the reaction product of a sulphide of the groupconsisting" of hydrogen, sulphide-and sodium sulphide on a diazotizedprimary arylamine of the group con sisting of anthranilic acid, aniline,toluidines,. xylidines, and benzylamine, said reaction product as aprecipitate being dissolved in Watercontaim ing triethanolamine. f

' FREDERICK F. REISINGER;

REFERENCES CITED The following references are of record in the file ofthis patent:

7. AN ELECTRODEPOSITION PATH INCLUDING COPPER CYANIDE, SODIUM HYDROXIDE,AND THE REACTION PRODUCT OF A SULPHIDE OF THE GROUP CONSISTING OFHYDROGEN SULPHIDE AND SODIUM SULPHIDE ON A DIAZOTIZED PRIMARY ARYLAMINEOF THE GROUP CONSISTING OF ANTHRANILIC ACID, ANILINE, TOLUIDINES AS APRECIPITATE BEING DISSOLVED IN WATER CONTAINING TRIETHANOLAMINE.